GUATEMALA CITY (AP) _ Worn down by decades of military dictatorships and failed attempts at democracy, some Guatemalans now worry that their newly elected president and his party will be too powerful.

Reform-minded businessman Alvaro Arzu defeated fellow conservative Alfonso Portillo of the Guatemalan Republican Front in Sunday's elections. In addition, the president-elect's Advanced National Party _ known by its acronym PAN _ now controls Congress and 108 out of 300 mayoral slots.

One party that holds that much authority reminds many Guatemalans of the past.

Guatemala has been ruled by military dictators since an experiment with civilian rule in the 1940s was derailed by a U.S.-backed right-wing coup. In 1986, another civilian, Vinico Cerezo, came to power with a legislative majority.

But that experiment with democracy, too, was less than successful, said Manfredo Marroquin, of the Myrna Mack Foundation think tank. ``Congress during Cerezo's rule became a tool to merely approve the president's orders and gave way to outrageous levels of corruption,'' he said.

Marroquin said PAN's victory could be risky, because the party now controls the presidency, 42 of 80 legislative seats and local districts.

The rest of Congress is divided among three parties: the Guatemalan Republican Front, the leftist New Guatemala Democratic Front and a three-party coalition called the Democratic Alliance.

Guatemalans are particularly wary of presidential power because the last elected president, Jorge Serrano, tried to seize near-dictatorial power in May 1993 by shutting the courts and Congress.

Protests by business leaders eventually persuaded the army to push Serrano into exile a month later. Since then, Ramiro de Leon Carpio, a former human rights prosecutor, has governed as a caretaker president.

Arzu, who gained a reputation for honesty and efficiency as the capital's mayor, replaces de Leon when he begins a four-year term Sunday. He has vowed to govern by consensus and include opposition parties and organized civilian groups, such as unions and Mayan Indian organizations, in decisions.

Political experts hope Arzu keeps his promise. One, Mario Minera, cautioned that if PAN does not work with other parties and groups, governing will become impossible within six months.

Others were more optimistic.

``The PAN is a modern party not linked to a past of dictatorships and massacres. Most of the party people are educated and business-minded,'' said Gabriel Aguilera, of the Latin American Faculty of Social Sciences.

Miguel Angel Balcarcel, an independent analyst, noted that the recent elections were free of fraud. He said Arzu has pledged to reach a peace agreement with leftist guerrillas who have been fighting the government for 35 years.

These factors, he said, signal ``an historic change in Guatemala. ... The political path of transition is opening anew. The Advanced National Party must use its control to consolidate the opening.''

But rights activist Ronalth Ochaeta sees Arzu's victory as ``a mixed blessing, which could have positive results so long as power does not go to their heads, because power corrupts and that sometimes can be extremely dangerous.''

Arzu is expected to announce Cabinet posts Thursday.